They insisted the country was committing genocide by design, with more than 23,000 people having been killed in the war, according to the Hamas-run Gazan health ministry.
UK Foreign Secretary Lord Cameron has said it is "nonsense" for South Africa to accuse Israel of genocide amid its war with Hamas.
According to Sky News, a two-day hearing took place in the United Nations' International Court of Justice earlier this week, with South African lawyers saying the conflict in Gaza was part of decades of Israeli oppression.
They insisted the country was committing genocide by design, with more than 23,000 people having been killed in the war, according to the Hamas-run Gazan health ministry.
But Israel has vehemently denied the accusations, pointing to the 7 October attack, when Hamas fighters killed about 1,200 people and abducted around 250 - with around half of the hostages now released.
Asked by Sky News' Trevor Philips whether Israel had a case to answer, Lord Cameron said: "No, I absolutely don't. I think the South African action is wrong, I think it is unhelpful, I think it shouldn't be happening.
"Now of course I am not a lawyer, but they are talking here about genocide, they are taking this case on the basis of genocide and to prove that you have got to prove that there was intent."
The foreign secretary added: "I take the view that Israel is acting in self defence after the appalling attack on 7 October.
"But even if you take a different view to my view, to look at Israel, a democracy, a country with the rule of law, a country with armed forces that are committed to obeying the rule of law, to say that that country, that leadership, that armed forces, that they have intent to commit genocide, I think that is nonsense, I think that is wrong."
Labour's shadow health secretary, Wes Streeting, also appeared to criticise the case, telling Sky News it was "a distraction from what needs to happen, which is the diplomatic heavy lifting to bring about an end to this conflict".
He said South Africa was "perfectly entitled" to bring forward the case, and it was for the UN court to "weigh up" the evidence it is presented with.
"But I actually think the priority here has got to be trying to get to where we were actually some months ago now, which is a humanitarian pause in fighting and the diplomatic heavy lifting to bring about the conditions for sustainable ceasefire, which is what we all want to see," Mr Streeting added.
"You look at the scale of the bloodshed, you look at the scale of destruction in Gaza, the number of civilian casualties. They are disproportionate, and it's horrible."
It could take years for the court to make its ruling, but any ruling would be considered legally binding. However, it is unclear if Israel would comply.
If it doesn't, it could face UN sanctions - though there's a chance a US veto could block them.